1. Field of the Invention
The present invention relates to a system for automatically dimming vehicle high beam head lamps and more particularly to a system which includes an improved optical system and an image processing system, the optical system being adapted to discriminate both the horizontal and vertical position of light rays within a predetermined field of view and spatially segregate the light rays on a pixel sensor array in order to provide improved discrimination of vehicle head lamps and vehicle tail lamps relative to other ambient light sources. The image processing system provides further discrimination of ambient light sources in order to automatically dim vehicle head lamp high beams as a function of the angular position of another vehicle relative to the control vehicle.
2. Description of the Prior Art
Regulations set forth by the United States Department of Transportation (DOT) regulate the light emissions of vehicle high beam head lamps. Various state regulations are used to control the amount of glare experienced by drivers of other vehicles whether the vehicle is traveling in the same direction as the controlled vehicle or in an opposite direction.
Known vehicle high beam head lamp emissions in accordance with the DOT regulations provide an intensity of 40,000 cd at 0 degrees, 10,000 cd at 3 degrees, 3250 cd at 6 degrees, 1500 cd at 9 degrees and 750 cd at 12 degrees. An example of such an emission pattern is illustrated in FIG. 1. In order to avoid an illuminance of 0.5 foot candles (fc) incident on another vehicle, the vehicle high beam head lamps should be dimmed within 230 feet of another vehicle at 0 degrees, 115 feet of another vehicle at a horizontal position of 3 degrees relative to the datum, and 65 feet in the position of the other vehicle is 6 degrees relative to the controlled vehicle.
Various known head light dimmer control systems are known in the art. In order to prevent the drivers of other vehicles from being subjected to excessive glare levels, such automatic head lamp dimmer systems must sense both the head lights as well as the tail lights of other vehicles. While many known systems are adequately able to detect head lamps of oncoming vehicles, such systems are known to inadequately sense tail lights of vehicles traveling ahead of the control vehicle. As such, such systems are not able to automatically dim the high beam head lamps in time to prevent drivers of the vehicles travelling in the same direction as the controlled vehicle being subjected to excessive glare levels.
U.S. Pat. No. 5,537,003 assigned to the same assignee of the present invention discloses an automatic head lamp dimming system which includes an optical system for sensing tail lamps as well as head lamps. The '003 patent discloses a single photo diode with a mechanical scanning arrangement for scanning a predetermined field of view. Although the system provides relatively suitable sensing of head lamps as well as tail lamps, the optical subsystem is rather complicated and expensive to manufacture.